Electrolytic condenser



Sept. 3, 1949 c. DE LANGE ET A1. 2,233,209

ELECTROLYTIC CONDENSER Filed April 26, 1959 Patented Sept. 3, 1940UNITED STATES PATENT OFFICE ELECTROLYTIC' CONDENSER Application April26, 1939, Serial No. 270,267 In Germany May 30, 1938 1 Claim.

This invention relates to an electrolytic condenser having a cathodebody located within a tubular anode, and more particularly to anelectrolytic condenser comprising two condenser 5 units.

The term anode as used herein is to be understood to mean an electrodewhich is provided with an oxide iilm serving as a dielectric, and theterm cathode is to be understood to mean l that part or parts whichconstitute a. current supply conductor for the electrolyte.

It has been suggested, for example in the U. S. Patent 2,130,073 to deLangeet al., to give the anode of an electrolytic condenser a tubular lshape and to house therein a second tubular member which is closed atthe lower end and acts as a cathode. Although such a construction makesit possible to produce a condenser having the lowest possibleseries-resistance, there is a )o large amount of unused space inside thetubular cathode. In this patent it has also been proposed to utilize atleast a major portion of this space by housing a second completecondenser unit therein, and thereby form a condenser comis prising twounits each having their own electrodes.

The main object of our invention is to produce a simpler and lessexpensive condenser assembly of the above general type.

l0 A further object is to produce a condenser assembly which may be usedin cases where two condenser units are required, for example, forsmoothing the direct current supplied to the eld coil of anelectro-dynamic speaker.

35 A further object is to reduce the size of and the amount of materialused in such condenser assemblies.

A still further object is to produce a multiple condenser of the abovetype in which the con- 0 denser units have a common cathode andelectrolyte.

Further objects and advantages of the invention will appear as thedescription progresses.

In accordance with the invention we locate 45 within the inner tubularcathode a second nlmforming electrode which forms with said cathode asecond condenser unit having a separate anode vsupply connection. Inthis manner the space ,f within the irst condenser unit is efficiently50 utilized, and theinner surface of the tubular cathode is also used.The film-forming electrode, or internal anode, is arranged with itssurface close to the inner surface of the tubular cathode with theresult that this second conla denser unit has a low series resistance,and the series resistance can be further decreased by giving thenlm-forming electrode a shape corresponding to that of the cathode.

In one embodiment of the invention the internal anode is shaped as ahollow cylinder to 5 reduce the weight as much as possible, and isprovided with slots to form short paths for the iiow of current throughthe electrolyte from the cathode to the inner surface of the internalanode.

The condenser according to the invention can be so constructed that thesupply connection for the internal anode may be at either end of thecondenser, and this connection -as well as the connection for the firstanodemay be at the same end.

In order that the invention may be clearly understood and readilycarried into effect, We shall describe the same in more detail withreference to the accompanying drawing in which: 2@

Fig. l is a sectionized viewof a condenser according to the invention,and

Fig. 2 is a sectionized View of a condenser according to anotherembodiment of the invention.

The condenser illustrated in Figure 1 com- 25 prises a cylindricalcathode-container I of aluminium whose upper end forms a dome 2 providedwith several vent holes 3 and having a tubular extension 4. The bottomedge of container I is spun over the edge of a member 5 30 of insulatingmaterial, such as Bakelite, with the interposition of a gasket 6, forinstance of rubber. Member 5 has a threaded tubularportion 7 forsecuring the condenser to a support and its upper surface is corrugated.

Within the container I is a cup-shaped anode 8, for instance ofaluminum, having a rodshaped extension 9 passing through a bore inmember 5. The end of the extension 9 is riveted over at I I with theinterposition of a terminal IU, whereby a liquid-tight seal is madebetween the bottom of anode 8 and the corrugated upper surface of member5 by means of the gasket 6.

Secured to the top of container I by several rivets 48 is a cup-shapedcathode I2 which extends within the anode 8 with its outer surfaceparallel to the inner surface of the anode. Instead of being riveted,the cathode I2 may be spot Welded to the container I, and if the cathodeI2 is 50 made by extrusion, small projections may be formed on its uppersurface and used as rivets.

Within cathode I2 is a second or internal anode I3 of cup-shape whichhas a rod-shaped extension I4 passing through the tubular pro- 35jection 4. A tubular'gasket I5, for

instance of rubber, is placed over extension I8, and the projection 4 isgrooved, for instance by rolling, at IEA to effect a liquid-tight sealand a supporting connection. If?. desired the extension 4 may beprovided with a plurality of groovings I 5A. The anode I3 is providedwith a plurality of slots I6, for instance saw-cuts, to reduce the pathsof the current owing from the inner surface of cathode I2 to the innersurface of anode I3.

The vessel I is filled to a level above the anode I3 by a suitableelectrolyte Il for instance a mixture of 240 grams of boric acid(HsBOa), 1,000 grams of ethylene glycol, 30 c.c. of ammonia (NHiOH) and1,000 c.c. of water.

To prevent corrosion of the non-formed parts in contact with theelectrolyte, both surfaces of cathode I2 and the inner surface of thecontainer I may be chromium plated.

'To increase the surface area and hence the capacity, the surfaces ofanodes 8 and I3 are preferably etched by any of the methods kno-w in theart.

A band I8 of flexible material, such as rubber, surrounds the dome 2 andnormally closes the vent holes 3. During operation of the condenser thegases produced within the container I escape through holes 3 in knownmanner. To asorb any electrolyte which may be carried out through holes3 by the escaping gases, a mass of absorbent material I9, such assaw-dust or cottonwool, is located within a cover 20 secured, forinstance Welded, to container I, and provided with an aperture 2|.

A condenser of the construction shown is very compact and has extremelydesirable electric properties.

When the two electrodes 8 and I3 are etched,

.they can supply an extremely large capacity.

For example, if the external anode 8 has a diameter of 24.5 mm. and aheight 80 mm., it will have a capacity of 16 microfarads at a workingvoltage of 450 volts, and if the internal anode I3 has a diameter of17.5 mm. and a height of 80 mm. it will supply a capacity of 16microfarads at a working voltage of 300 to 320 volts. Since the spacingbetween the active surfaces is very small, as appears from the diametersgiven above, the series resistance has a very low value and thealternating current load may be increased to a high value. If thecondenser illustrated is used in a smoothing system and the externalcondenser unit is connected directly after the rectifier, i. e. thecondenser unit which is calculated for the highest lworking voltage andhas the electrode 8 as an anode, a superimposed alternating currentvoltage of at least 45 volts is admissible.

In the condenser illustrated in Figure 1 the connection for the externalanode 8 leaves through the lower end of the assembly and the connectionfor the internal anode I3 leaves through the upper end. However, theinvention can also be carried into eifect witha construction in whichthe connections to both anodes leave at the same end, and such aconstruction is illustrated in Figure 2.

The condenser illustrated in Figure 2 comprises a cup-shapedcathode-container 23, for instance of aluminum, whose closed end isformed as a dome 2li provided with a plurality of vent holes 25. Thebottom end of container 23 is spun over the edge of a tubular member 26of insulating material, such als Bakelitef .with the interposition of agasket 2l, for instance of rubber, to form a liquid-tight joint.

Within container 23 is a cup-shaped external anode 28 of a film-formingmetal, such as aluminum, which has a tubular extension .29 passingthrough the bore of member 26. The end of extension 29 riveted over upona shoulder of member 25 with the interposition of a terminal 38.

A cathode 3| in the form of a cylinder of aluminum has a flared upperend which is secured, for instance welded, to the container I.

A second or internal anode 32 in the form of a cylinder of aluminumprovided with several saw-cuts 33, has a rod-shaped portion 34, ex-

tending throughthe bore of the extension 29 of anode 28. A bushing 44,for instance of rubber, is disposed between portion 3f! and extension 29and serves to provide a liquid-tight seal and also to insulate anode 32from anode 28.

The bottom end of portion 34 is riveted over upon a bushing 35, forinstance of Bakelite, which bears upon the end of anode 28 at 36. Aterminal 3l for anode 32 is secured at this riveted. joint.

As described in connection with Figure l, a rubber band I6 normallycloses the vent holes 25, and a ring 38 of liquid-absorbent material,such as cotton Wool, located within a cover 39 secured to container 23,for instance by welding, serves to absorb any escaping electrolyte.Cover 39 is provided with a vent hole 40.

In order that possible displacement of the electrodes will not result ina short circuit, We prefer to provide anodes 28 and 32 and cathode 3|with bands 4| of insulating material, such as rubber.

We wish it to be understood that'we do not wish to be limited to theexact details of construction shown and described, because obviousmodiiications will readily occur to one skilled in the art.

What we claim is:

An electrolytic condenser comprising a cupshaped cathode-container, acup-shaped cathode supported from said container and forming an annularspace therewith, a cup-shaped anode having an active tubular portionextending into said space and forming a condenser unit with saidcathode, means insulatingly supporting said anode from the open end ofsaid container, a second cup-shaped anode having a tubular portionextending in closely-spaced relationship with the inner surface of saidcathode to form a second condenser unit therewith, means in-y CORNELISDE LANGE. JOHAN DIRK DE VRIES.

